Indole derivatives as dopamine D4 antagonists

ABSTRACT

The present invention accordingly provides the use of a compound of formula I, or a pharmaceutically acceptable salt thereof or a prodrug thereof: ##STR1## wherein R 1  represents hydrogen or C 1-6  alkyl; 
     Z represents --CH 2  -- or --CH 2  CH 2  --; 
     R 2  represents hydrogen, C 1-6  alkyl, C 1-6  alkoxy, aryl(C 1-6 )alkyl or halogen; 
     R 3 , R 4  and R 5  independently represent hydrogen, hydrocarbon, a heterocyclic group, halogen, cyano, trifluoromethyl, nitro, --OR a , --SR a , --SOR a , --SO 2  R a , --SO 2  NR a  R b , --NR a  R b , --NR a  COR b , --NR a  CO 2  R b , --COR a , --CO 2  R a  or --CONR a  R b  ; and 
     R a  and R b  independently represent hydrogen, hydrocarbon or a heterocyclic group; 
     for the manufacture of a medicament for the treatment and/or prevention of psychotic disorders such as schizophrenia.

This invention relates to a particular class of heteroaromatic compounds. More particularly, the invention is concerned with the use of substituted indole derivatives which are antagonists of dopamine receptor subtypes within the brain and are therefore of benefit in the treatment and/or prevention of psychotic disorders such as schizophrenia.

The "dopamine hypothesis" of schizophrenia predicts an increased activity of dopamine neurotransmission in the disease. The hypothesis is supported by early observations that drugs, such as amphetamine, with dopamine agonist or dopamine-releasing properties are capable of eliciting a psychosis indistinguishable from acute paranoid schizophrenia.

Schizophrenia is a disorder which is conventionally treated with drugs known as neuroleptics. In the majority of cases, the symptoms of schizophrenia can be treated successfully with so-called "classical" neuroleptic agents such as haloperidol. Classical neuroleptics generally are antagonists at dopamine D₂ receptors. The fact that classical neuroleptic drugs have an action on dopamine receptors in the brain thus lends credence to the "dopamine hypothesis" of schizophrenia.

Molecular biological techniques have revealed the existence of several subtypes of the dopamine receptor. The dopamine D₁ receptor subtype has been shown to occur in at least two discrete forms. Two forms of the D₂ receptor subtype, and at least one form of the D₃ receptor subtype, have also been discovered. More recently, the D₄ (Van Tol et al., Nature (London), 1991, 350, 610) and D₅ (Sunahara et al., Nature (London), 1991, 350, 614) receptor subtypes have been described.

Notwithstanding their beneficial antipsychotic effects, classical neuroleptic agents such as haloperidol are frequently responsible for eliciting acute extrapyramidal symptoms and neuroendocrine disturbances. These side-effects, which clearly detract from the clinical desirability of classical neuroleptics, are believed to be attributable to D₂ receptor blockade in the striatal region of the brain. It is considered (Van Tol et al., supra) that compounds which can interact selectively with the dopamine D₄ receptor subtype, whilst having a less-pronounced action at the D₂ subtype, might be free from, or at any rate less prone to, the side-effects associated with classical neuroleptics, whilst at the same time maintaining a beneficial level of antipsychotic activity.

The compounds of use in the present invention, being antagonists of dopamine receptor subtypes within the brain, are accordingly of benefit in the treatment and/or prevention of psychotic disorders such as schizophrenia. Moreover, the compounds of use in the invention have a selective affinity for the dopamine D₄ receptor subtype over other dopamine receptor subtypes, in particular the D₂ subtype, and can therefore expected to manifest fewer side-effects than those associated with classical neuroleptic drugs.

The compound 3-(1,2,3,4-tetrahydroisoquinolin-2-yl)methyl-1H-indole is described in Recl. Trav. Chim. Pays-Bas, 1954, 73, 629, and is stated to have oxytocic activity. There is, however, no suggestion therein that this compound might be an antagonist of dopamine receptor subtypes within the brain, and thus be of benefit in the treatment and/or prevention of psychotic disorders such as schizophrenia, still less that in doing so it might be expected to manifest fewer side-effects than those exhibited by classical neuroleptic agents.

The present invention accordingly provides the use of a compound of formula I, or a pharmaceutically acceptable salt thereof or a prodrug thereof: ##STR2## wherein R¹ represents hydrogen or C₁₋₆ alkyl;

Z represents --CH₂ -- or --CH₂ CH₂ --;

R² represents hydrogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, aryl(C₁₋₆)alkyl or halogen;

R³, R⁴ and R⁵ independently represent hydrogen, hydrocarbon, a heterocyclic group, halogen, cyano, trifluoromethyl, nitro, --OR^(a), --SR^(a), --SOR^(a), ---SO₂ R^(a), --SO₂ NR^(a) R^(b), --NR^(a) R^(b), --NR^(a) COR^(b), --NR^(a) CO₂ R^(b), --COR^(a), --CO₂ R^(a) or --CONR^(a) R^(b) ; and

R^(a) and R^(b) independently represent hydrogen, hydrocarbon or a heterocyclic group;

for the manufacture of a medicament for the treatment and/or prevention of psychotic disorders such as schizophrenia.

For use in medicine, the salts of the compounds of formula I will be pharmaceutically acceptable salts. Other salts may, however, be useful in the preparation of the compounds of use in the invention or of their pharmaceutically acceptable salts. Suitable pharmaceutically acceptable salts of the compounds of use in this invention include acid addition salts which may, for example, be formed by mixing a solution of the compound of use in the invention with a solution of a pharmaceutically acceptable acid such as hydrochloric acid, sulphuric acid, fumaric acid, maleic acid, succinic acid, acetic acid, benzoic acid, oxalic acid, citric acid, tartaric acid, carbonic acid or phosphoric acid. Furthermore, where the compounds of use in the invention carry an acidic moiety, suitable pharmaceutically acceptable salts thereof may include alkali metal salts, e.g. sodium or potassium salts; alkaline earth metal salts, e.g. calcium or magnesium salts; and salts formed with suitable organic ligands, e.g. quaternary ammonium salts.

The term "hydrocarbon" as used herein includes straight-chained, branched and cyclic groups containing up to 18 carbon atoms, suitably up to 15 carbon atoms, and conveniently up to 12 carbon atoms. Suitable hydrocarbon groups include C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₇ cycloalkyl, C₃₋₇ cycloalkyl(C₁₋₆)alkyl, aryl, aryl(C₁₋₆)alkyl, aryl(C₂₋₆)alkenyl and aryl(C₂₋₆)alkynyl.

The expression "a heterocyclic group" as used herein includes cyclic groups containing up to 18 carbon atoms and at least one heteroatom preferably selected from oxygen, nitrogen and sulphur. The heterocyclic group suitably contains up to 15 carbon atoms and conveniently up to 12 carbon atoms, and is preferably linked through carbon. Examples of suitable heterocyclic groups include C₃₋₇ heterocycloalkyl, C₃₋₇ heterocycloalkyl(C₁₋₆)alkyl, heteroaryl, heteroaryl(C₁₋₆)alkyl, heteroaryl(C₂₋₆)alkenyl and heteroaryl(C₂₋₆)alkynyl groups.

Suitable alkyl groups within the scope of the term "hydrocarbon" and within the definition of the substituents R¹ and R² include straight-chained and branched alkyl groups containing from 1 to 6 carbon atoms. Typical examples include methyl and ethyl groups, and straight-chained or branched propyl and butyl groups. Particular alkyl groups are methyl, ethyl, n-propyl, isopropyl and t-butyl.

Suitable alkenyl groups within the scope of the term "hydrocarbon" include straight-chained and branched alkenyl groups containing from 2 to 6 carbon atoms. Typical examples include vinyl and allyl groups.

Suitable alkynyl groups within the scope of the term "hydrocarbon" include straight-chained and branched alkynyl groups containing from 2 to 6 carbon atoms. Typical examples include ethynyl and propargyl groups.

Suitable cycloalkyl groups include groups containing from 3 to 7 carbon atoms. Particular cycloalkyl groups are cyclopropyl and cyclohexyl.

Particular aryl groups within the scope of the term "hydrocarbon" include phenyl and naphthyl.

Particular aryl(C₁₋₆)alkyl groups within the scope of the term "hydrocarbon" and within the definition of the substituent R² include benzyl, naphthylmethyl, phenethyl and phenylpropyl.

Suitable heterocycloalkyl groups include azetidinyl, pyrrolidyl, piperidyl, piperazinyl and morpholinyl groups.

Suitable heteroaryl groups within the scope of the expression "a heterocyclic group" include pyridyl, quinolyl, isoquinolyl, pyridazinyl, pyrimidinyl, pyrazinyl, pyranyl, furyl, benzofuryl, dibenzofuryl, thienyl, benzthienyl, indolyl, indazolyl, imidazolyl, benzimidazolyl, oxadiazolyl and thiadiazolyl groups.

Particular heteroaryl(C₁₋₆)alkyl groups within the scope of the expression "a heterocyclic group" include thienylmethyl, thienylethyl, furylethyl, pyridylmethyl, pyridylethyl, pyrimidinylmethyl and pyrazinylmethyl.

The hydrocarbon and heterocyclic groups may in turn be optionally substituted by one or more groups selected from C₁₋₆ alkyl, adamantyl, phenyl, aryl(C₁₋₆)alkyl, halogen, C₁₋₆ haloalkyl, C₁₋₆ aminoalkyl, trifluoromethyl, hydroxy, C₁₋₆ alkoxy, aryloxy, keto, C₁₋₃ alkylenedioxy, nitro, cyano, carboxy, C₂₋₆ alkoxycarbonyl, C₂₋₆ alkoxycarbonyl(C₁₋₆)alkyl, C₂₋₆ alkylcarbonyloxy, arylcarbonyloxy, C₂₋₆ alkylcarbonyl, arylcarbonyl, C₁₋₆ alkylthio, C₁₋₆ alkylsulphinyl, C₁₋₆ alkylsulphonyl, arylsulphonyl, --NR^(v) R^(w), --NR^(v) COR^(w), --NR^(v) CO₂ R^(w), --NR^(v) SO₂ R^(w), --CH₂ NV^(v) SO₂ R^(w), --NHCONR^(v) R^(w), --CONR^(v) R^(w), --SO₂ NR^(v) R^(w) and --CH₂ SO₂ NR^(v) R^(w) in which R^(v) and R^(w) independently represent hydrogen, C₁₋₆ alkyl, aryl or aryl(C₁₋₆)alkyl.

The term "halogen" as used herein includes fluorine, chlorine, bromine and iodine, especially chlorine.

The present invention includes within its scope the use of prodrugs of the compounds of formula I above. In general, such prodrugs will be functional derivatives of the compounds of formula I which are readily convertible in vivo into the required compound of formula I. Conventional procedures for the selection and preparation of suitable prodrug derivatives are described, for example, in "Design of Prodrugs", ed. H. Bundgaard, Elsevier, 1985.

Where the compounds of use in the invention have at least one asymmetric centre, they may accordingly exist as enantiomers. Where the compounds of use in the invention possess two or more asymmetric centres, they may additionally exist as diastereoisomers. It is to be understood that the use of all such isomers and mixtures thereof is encompassed within the scope of the present invention.

Suitably, the substituent R¹ represents hydrogen or methyl, especially hydrogen.

Particular values of R² include hydrogen, methoxy, chloro and bromo.

Suitable values for the substituents R³, R⁴ and R⁵ include hydrogen, halogen, cyano, nitro, trifluoromethyl, amino, C₁₋₆ alkylamino, di(C₁₋₆)alkylamino, C₁₋₆ alkyl, C₁₋₆ alkoxy, aryl(C₁₋₆)alkoxy and C₂₋₆ alkylcarbonyl. Particular values include hydrogen, fluoro, chloro, methyl, ethyl, methoxy and benzyloxy.

Specific compounds of use in the present invention include: 3-(1,2,3,4-tetrahydroisoquinolin-2-yl)methyl-1H-indole; and pharmaceutically acceptable salts thereof and prodrugs thereof.

Certain compounds falling within the definition of formula I above are novel. In a further aspect, therefore, the present invention provides a compound of formula II, or a salt or prodrug thereof: ##STR3## wherein R¹¹ represents hydrogen or C₁₋₆ alkyl;

Z represents --CH₂ -- or --CH₂ CH₂ --;

R¹² represents hydrogen, C₁₋₆ alkyl, C¹⁻⁶ alkoxy, aryl(C₁₋₆)alkyl or halogen;

R¹³, R¹⁴ and R¹⁵ independently represent hydrogen, hydrocarbon, a heterocyclic group, halogen, cyano, trifluoromethyl, nitro, --OR^(a), --SR^(a), --SOR^(a), --SO₂ R^(a), --SO₂ NR^(a) R^(b), --NR^(a) R^(b), --NR^(a) COR^(b), --NR^(a) CO₂ R^(b), --COR^(a), --CO₂ R^(a) or --CONR^(a) R^(b) ; and

R^(a) and R^(b) independently represent hydrogen, hydrocarbon or a heterocyclic group;

provided that, when Z is --CH₂ CH₂ --, then R¹¹, R¹², R¹³, R¹⁴ and R¹⁵ are not simultaneously hydrogen.

Subject to the above proviso, the substituents R¹¹ to R¹⁵ in the compounds of formula II correspond to the substituents R¹ to R⁵ respectively as defined with reference to the compounds of formula I.

Specific novel compounds within the scope of the present invention include:

6-fluoro-3-(1,2,3,4-tetrahydroisoquinolin-2-yl)methyl-1H-indole;

3-(5-chloro-1,2-dihydroisoindol-2-yl)methyl-1H-indole;

3-(5-bromo-1,2-dihydroisoindol-2-yl)methyl-1H-indole;

3-(5-methoxy-1,2-dihydroisoindol-2-yl)methyl-1H-indole;

3-(4-chloro-1,2-dihydroisoindol-2-yl)methyl-1H-indole;

3-(4-methoxy-1,2-dihydroisoindol-2-yl)methyl-1H-indole;

3-(1,2-dihydroisoindol-2-yl)methyl-1H-indole; and salts and prodrugs thereof.

The invention also provides pharmaceutical compositions comprising one or more of the novel compounds according to the invention in association with a pharmaceutically acceptable carrier. Preferably these compositions are in unit dosage forms such as tablets, pills, capsules, powders, granules, sterile parenteral solutions or suspensions, metered aerosol or liquid sprays, drops, ampoules, auto-injector devices or suppositories; for oral, parenteral, intranasal, sublingual or rectal administration, or for administration by inhalation or insufflation. Alternatively, the compositions may be presented in a form suitable for once-weekly or once-monthly administration; for example, an insoluble salt of the active compound, such as the decanoate salt, may be adapted to provide a depot preparation for intramuscular injection. For preparing solid compositions such as tablets, the principal active ingredient is mixed with a pharmaceutical carrier, e.g. conventional tableting ingredients such as corn starch, lactose, sucrose, sorbitol, talc, stearic acid, magnesium stearate, dicalcium phosphate or gums, and other pharmaceutical diluents, e.g. water, to form a solid preformulation composition containing a homogeneous mixture of a compound of the present invention, or a pharmaceutically acceptable salt thereof. When referring to these preformulation compositions as homogeneous, it is meant that the active ingredient is dispersed evenly throughout the composition so that the composition may be readily subdivided into equally effective unit dosage forms such as tablets, pills and capsules. This solid preformulation composition is then subdivided into unit dosage forms of the type described above containing from 0.1 to about 500 mg of the active ingredient of the present invention. The tablets or pills of the novel composition can be coated or otherwise compounded to provide a dosage form affording the advantage of prolonged action. For example, the tablet or pill can comprise an inner dosage and an outer dosage component, the latter being in the form of an envelope over the former. The two components can be separated by an enteric layer which serves to resist disintegration in the stomach and permits the inner component to pass intact into the duodenum or to be delayed in release. A variety of materials can be used for such enteric layers or coatings, such materials including a number of polymeric acids and mixtures of polymeric acids with such materials as shellac, cetyl alcohol and cellulose acetate.

The liquid forms in which the novel compositions of the present invention may be incorporated for administration orally or by injection include aqueous solutions, suitably flavoured syrups, aqueous or oil suspensions, and flavoured emulsions with edible oils such as cottonseed oil, sesame oil, coconut oil or peanut oil, as well as elixirs and similar pharmaceutical vehicles. Suitable dispersing or suspending agents for aqueous suspensions include synthetic and natural gums such as tragacanth, acacia, alginate, dextran, sodium carboxymethylcellulose, methylcellulose, polyvinyl-pyrrolidone or gelatin.

In the treatment of schizophrenia, a suitable dosage level is about 0.01 to 250 mg/kg per day, preferably about 0.05 to 100 mg/kg per day, and especially about 0.05 to 5 mg/kg per day. The compounds may be administered on a regimen of 1 to 4 times per day.

The compounds of formula I above, including the novel compounds in accordance with the present invention, may be prepared by a process which comprises reacting a compound of formula III with a compound of formula IV: ##STR4## wherein R², R³, R⁴, R⁵ and Z are as defined above, and R^(p) corresponds to the group R¹ as defined above or represents a suitable protecting group; in the presence of a substantially equimolar amount of formaldehyde; followed, where required, by removal of the protecting group R^(p) ; and subsequently, if necessary, N-alkylation by standard methods to introduce the moiety R¹.

The reaction is conveniently carried out by stirring the reactants in aqueous acetic acid, ideally in the presence of a buffer such as sodium acetate trihydrate, suitably at room temperature.

The formaldehyde may be utilised in the form of paraformaldehyde; or as a solution of formaldehyde in an inert solvent, e.g. 37% aqueous formaldehyde.

The protecting group R^(p), when present, is suitably an acyl moiety such as acetyl, which can conveniently be removed as necessary by treatment under strongly basic conditions, e.g. sodium methoxide in methanol. Alternatively, the protecting group R^(p) may be a carbamoyl moiety such as t-butoxycarbonyl (BOC), which can conveniently be removed as necessary by treatment under mildly acidic conditions.

In an alternative procedure, the compounds of formula I above, including the novel compounds according to the present invention, may be prepared by a process which comprises reacting a compound of formula IV as defined above with a compound of formula V: ##STR5## wherein R³, R⁴, R⁵ and R^(p) are as defined above, and L represents a suitable leaving group; followed, where required, by removal of the protecting group R^(p) ; and subsequently, if necessary, N-alkylation by standard methods to introduce the moiety R¹.

The leaving group L is suitably a halogen atom, e.g. chlorine or bromine; or a dialkylamino group, e.g. dimethylamino.

When L represents a halogen atom, the reaction 5 between compounds IV and V is conveniently carried out by stirring the reactants under basic conditions in a suitable solvent, for example potassium carbonate in N,N-dimethylformamide, or triethylamine in tetrahydrofuran or acetonitrile. Where L represents a dialkylamino group, the reaction is conveniently effected by heating the reactants in an inert solvent such as toluene, typically at the reflux temperature of the solvent.

Where they are not commercially available, the starting materials of formula III, IV and V may be prepared by standard methods well known from the art. For example, the 1,2-dihydroisoindole intermediates of formula IV wherein Z is --CH₂ -- may be prepared by methods analogous to those described in Org. Synth., Collect. Vol. 5, Wiley, 1973, p. 406; and in EP-A-0343560.

It will be appreciated that any compound of formula I initially obtained from any of the above processes may, where appropriate, subsequently be elaborated into a further desired compound of formula I using techniques known from the art. For example, a compound of formula I wherein R¹ is hydrogen initially obtained may be converted into a compound of formula I wherein R¹ represents C₁₋₆ alkyl by standard alkylation techniques, such as by treatment with an alkyl iodide, e.g. methyl iodide, typically under basic conditions, e.g. sodium hydride in dimethylformamide, or triethylamine in acetonitrile.

Where the above-described processes for the preparation of the compounds of use in the invention give rise to mixtures of stereoisomers, these isomers may be separated by conventional techniques such as preparative chromatography. The compounds may be prepared in racemic form, or individual enantiomers may be prepared either by enantiospecific synthesis or by resolution. The compounds may, for example, be resolved into their component enantiomers by standard techniques such as preparative HPLC, or the formation of diastereomeric pairs by salt formation with an optically active acid, such as (-)-di-p-toluoyl-d-tartaric acid and/or (+)-di-p-toluoyl-1-tartaric acid, followed by fractional crystallization and regeneration of the free base. The compounds may also be resolved by formation of diastereomeric esters or amides, followed by chromatographic separation and removal of the chiral auxiliary.

During any of the above synthetic sequences it may be necessary and/or desirable to protect sensitive or reactive groups on any of the molecules concerned. This may be achieved by means of conventional protecting groups, such as those described in Protective Groups in Organic Chemistry, ed. J. F. W. McOmie, Plenum Press, 1973; and T. W. Greene & P. G. M. Wuts, Protective Groups in Organic Synthesis, John Wiley & Sons, 1991. The protecting groups may be removed at a convenient subsequent stage using methods known from the art.

The following Examples illustrate the preparation of compounds according to the invention.

The compounds useful in this invention potently inhibit [³ H]-spiperone binding to human dopamine D₄ receptor subtypes expressed in clonal cell lines.

[³ H]-SPIPERONE BINDING STUDIES

Clonal cell lines expressing the human dopamine D₄ receptor subtype were harvested in PBS and then lysed in 10 mM Tris-HCl pH 7.4 buffer containing 5 mM MgSO₄ for 20 min on ice. Membranes were centrifuged at 50,000 g for 15 min at 4° C. and the resulting pellets resuspended in assay buffer (50 mM Tris-HCl pH 7.4 containing 5 mM EDTA, 1.5 mM CaCl₂, 5 mM MgCl₂, 5 mM KCl, 120 mM NaCl, and 0.1% ascorbic acid) at 20 mg/ml wet weight. Incubations were carried out for 60 min at room temperature (22° C.) in the presence of 0.05-2 nM [³ H]-spiperone or 0.2 nM for displacement studies and were initiated by addition of 20-100 μg protein in a final assay volume of 0.5 ml. The incubation was terminated by rapid filtration over GF/B filters presoaked in 0.3% PEI and washed with 10 ml ice-cold 50 mM Tris-HCl, pH 7.4. Specific binding was determined by 10 μM apomorphine and radioactivity determined by counting in a LKB beta counter. Binding parameters were determined by non-linear least squares regression analysis, from which the inhibition constant K_(i) could be calculated for each test compound.

The compounds of the accompanying Examples were tested in the above assay, and all were found to possess a K_(i) value for displacement of [³ H]-spiperone from the human dopamine D₄ receptor subtype of below 1.5 μM.

EXAMPLE 1 3-[1,2,-Dihydroindol-2-yl]methyl-1H-indole

To gramine (731 mgs, 4.2 mmol) in dry PhMe (20 ml) was added 1,2-dihydroisoindole (prepared as in Org. Syn., Coll. Vol. V, p. 406) (500 mgs, 4.2 mmol) and the reaction refluxed for 6 h. The solvent was evaporated, the residue triturated with PhMe and the resultant solid recrystallised from PhMe to yield the title compound (550 mgs, 52%). M.p. 168°-170° C.; (Found: C, 80.44; H, 6.46; N, 10.98. C₁₇ H₁₆ N₂.0.25H₂ O) requires C, 80.76; H, 6.38; N, 11.08%). δ_(H) (CDCl₃) 4.00 (4H, s, 2×isoindolinyl CH₂), 4.11 (2H, s, NCH₂ Ar), 7.08-7.23 (7H, m, ArH), 7.36 (1H, d, J 7.9 Hz, ArH), 7.77 (1H, d, J 7.9 Hz, ArH), 8.18 (1H, brs, NH); m/z (CI+, NH₃) 249 (M+1)+.

Other 1,2-Dihydroisoindoles (prepared as in EP 343560) were coupled with gramine as above to yield the following:

EXAMPLE 2 3-[4-Chloro-1,2-dihydroisoindol-2-yl]methyl-1H-indole

M.p. 163°-165° C. (PhMe); (Found: C, 72.36; H, 5.23; N, 9.74. C₁₇ H₁₅ CIN₂ requires C, 72.21; H, 5.35; N, 9.91%). δ_(H) (CDCl₃) 4.05 (4H, s, 2×isoindolinyl CH₂), 4.11 (2 H, s, NCH₂ Ar), 7.02-7.25 (6H, m, ArH), 7.38 (1H, d, J 8.0 Hz, ArH), 7.77 (1H, d, J 7.4 Hz, ArH), 8.11 (1H, brs, NH); m/z (CI+, NH₃) 283 (M+1)+.

EXAMPLE 3 3-[5-Bromo-1,2-dihydroisoindol-2-yl]methyl-1H-indole

M.p. 188°-190° C. (PhMe); (Found: C, 62.70; H, 4.58; N, 8.35. C₁₇ H₁₅ BrN₂ requires C, 62.40; H, 4.62; N, 8.56%). δ_(H) (CDCl₃) 3.99 (2H, s, isoindolinyl CH₂), 4.02 (2H, s, isoindolinyl CH₂), 4.13 (2H, s, NCH₂ Ar), 7.03 (1H, d, J 8.6 Hz, ArH), 7.11-7.25 (5H, m, ArH), 7.39 (1H, d, J 8.0 Hz, ArH), 7.72 (1H, d, J 8.0 Hz, ArH), 8.26 (1H, brs, NH); m/z (CI+, NH₃) 327 (M+).

EXAMPLE 4 3-[4-Methoxy- 1,2-dihydroisoindol-2-yl]methyl-1H-indole

M.p. 176°-179° C. (PhMe); (Found: C, 76.38; H, 6.38; N, 9.80. C₁₈ H₁₈ N₂ O.0.2H₂ O requires C, 76.68; H, 6.59; N, 9.93%). δ_(H) (CDCl₃) 3.71 (3H, s, OCH₃), 3.91 (2H, s, isoindolinyl CH₂), 3.95 (2H, s, isoindolinyl CH₂), 4.05 (2H, s, NCH₂ Ar), 6.62 (1H, d, J 8.2 Hz, ArH), 6.69 (1H. d,J 7.4 Hz, ArH), 6.98 (1H, t, J 6.9 Hz, ArH), 7.04-7.09 (2H, m, ArH), 7.32 (1H, d, J 8.0 Hz, ArH), 7.46 (1H, s, ArH), 7.64 (1H, d, J 7.8 Hz, ArH),10.02 (1H, brs, NH); m/z CI+, NH₃) 279 (M+1)+.

EXAMPLE 5 3-[5-Methoxy-1,2-dihydroisoindol-2-yl]methyl-1H-indole

M.p. 178°-180° C. (PhMe); (Found: C, 77.93; H, 6.41; N, 9.70. C₁₈ H₁₈ N₂ 0 requires C, 77.67; H, 6.52; N, 10.06%). δ_(H) (CDCl₃) 3.68 (3H, s, OCH₃), 3.82 (2H, s, isoindolinyl CH₂), 3.85 (2H, s, isoindolinyl CH₂), 3.99 (2H, s, NCH₂ Ar), 6.62 (1H, s, 4'-H), 6.95-7.18 (4H, m, ArH), 7.30 (1H, d, J 7.4 Hz, ArH), 7.64 (1H, d, J 7.8 Hz, ArH), 10.03 (1H, brs, NH); m/z (CI+, NH₃) 279 (M+1)+.

EXAMPLE 6 3-[5-Chloro-1,2-dihydro-isoindol-2-yl]methyl-1H-indole

M.p. 192°-194° C. (dec.) (PhMe); (Found: C, 72.54; H, 5.39; N, 9.94. C₁₇ H₁₅ CIN₂ requires C, 72.21; H, 5.35; N, 9.91%); δ_(H) (DMSO-d₆) 3.82 (4H, brs, 2×isoindolinyl CH₂), 3.98 (2H, s, NCH₂ Ar), 6.97 (1 H, m, ArH), 7.07 (1H, m, ArH), 7.20 (2H, m, ArH), 7.29 (2H, m, ARH), 7.36 (1H, d, J 8 Hz, 7-H), 7.64 (1H, d, J 8 Hz, 4-H), 10.93 (1H, brs, NH); m/z (CI+, NH₃) 283 (M+1)+.

EXAMPLE 7 6-Fluoro-3-(1,2,3,4-tetrahydroisoquinolin-2-yl methyl)indole

M.p. 144°-145° C. (EtOAc); (Found: C, 77.32; H, 6.22; N, 10.04. C₁₈ H₁₇ FN₂ requires C, 77.12; H, 6.11; N, 9.99%); δ_(H) (CDCl₃) 2.68 (2H, t, J 5.6 Hz, CH₂), 2.78 (2H, t, J 5.6 Hz, CH₂), 3.55 (2H, s, CH₂ N), 3.77 (2H, s, CH₂ N), 6.81 (1H, ddd, J 11.0, 9.7, 2.3 Hz, ArH), 6.97-7.14 (5H, m, ArH), 7.28 (1H, d, J 2.0 Hz, ArH), 7.63 (1H, dd, J 8.7, 5.7 Hz, ArH) and 11.00 (1H, s, NH); m/z (CI+, NH₃) 281 (M+1)+. 

We claim:
 1. A compound of formula II, or a pharmaceutically acceptable salt thereof: ##STR6## wherein R¹¹ represents hydrogen or C₁₋₆ alkyl;Z represents --CH₂ -- or --CH₂ CH₂ --; R¹² represents hydrogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, aryl (C₁₋₆) alkyl or halogen; R¹³, R¹⁴ and R¹⁵ independently represent hydrogen, hydrocarbon, a heterocyclic group, halogen, cyano, trifluoromethyl, nitro, --OR^(a), --SR^(a), --SOR^(a), --SO₂ R^(a), --SO₂ NR^(a) R^(b), --NR^(a) R^(b), --NR^(a) COR^(b), --NR^(a) CO₂ R^(b), --COR^(a), --CO₂ R^(a) or --CONR^(a) R^(b) ; and R^(a) and R^(b) independently represent hydrogen, hydrocarbon or a heterocyclic group;wherein in each case "hydrocarbon" represents straight-chained, branched and cyclic groups containing up to 18 carbon atoms and "heterocyclic" represents C₃₋₇ heterocycloalkyl, C₃₋₇ heterocycloalkyl (C₁₋₆) alkyl, heteroaryl, heteroaryl (C₁₋₆) alkyl, heteroaryl (C₂₋₆) alkenyl and heteroaryl (C₂₋₆) alkynyl groups, wherein "heteroaryl" represents pyridyl, quinolyl, isoquinolyl, pyridazinyl, pyrimidinyl, pyrazinyl, pyranyl, furyl, benzofuryl, dibenzofuryl, thienyl, benzthienyl, indolyl, indazolyl, imidazolyl, benzimidazolyl, oxadiazolyl and thiadiazolyl; provided that, when Z is --CH₂ CH₂ --, then R¹¹, R¹², R¹³, R¹⁴ and R¹⁵ are not simultaneously hydrogen.
 2. A compound as claimed in claim 1 wherein R¹² represents hydrogen, methoxy, chloro or bromo.
 3. A compound as claimed in claim 1 selected from:6-fluoro-3-(1,2,3,4-tetrahydroisoquinolin-2-yl)methyl-1H-indole; 3-(5-chloro-1,2-dihydroisoindol-2-yl)methyl-1H-indole; 3-(5-bromo-1,2-dihydroisoindol-2-yl)methyl-1H-indole; 3-(5-methoxy-1,2-dihydroisoindol-2-yl)methyl-1H-indole; 3-(4-chloro-1,2-dihydroisoindol-2-yl)methyl-1H-indole; 3-(4-methoxy-1,2-dihydroisoindol-2-yl)methyl-1H-indole; 3-(1,2-dihydroisoindol-2-yl)methyl-1H-indole; or a pharmaceutically acceptable prodrugs thereof.
 4. A pharmaceutical composition comprising a compound as claimed in claim 1 in association with a pharmaceutically acceptable carrier.
 5. A method for the treatment and/or prevention of psychotic disorders, which comprises administering to a patient in need of such treatment an effective amount of a compound as claimed in claim
 1. 6. A method of treatment and/or prevention of psychotic disorders comprising the administration of a compound of formula I, or a pharmaceutically acceptable salt thereof: ##STR7## wherein R¹ represents hydrogen or C₁₋₆ alkyl;Z represents --CH₂ -- or --CH₂ CH₂ --; R² represents hydrogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, ary(C₁₋₆) alkyl or halogen; R³, R⁴ and R⁵ independently represent hydrogen, hydrocarbon, a heterocyclic group, halogen, cyano, trifluoromethyl, nitro, --OR^(a), --SR^(a), --SOR^(a), --SO₂ R_(a), --SO₂ NR^(a) R^(b), --NR^(a) R^(b), --NR^(a) COR^(b), --NR^(a) CO₂ R^(b), --COR^(a), --CO₂ R^(a) or --CONR^(a) R^(b) ; and R^(a) and R^(b) independently represent hydrogen, hydrocarbon or a heterocyclic group;wherein in each case "hydrocarbon" represents straight-chained, branched and cyclic groups containing up to 18 carbon atoms and "heterocyclic" represents C₃₋₇ heterocycloalkyl, C₃₋₇ heterocycloalkyl (C₁₋₆) alkyl, heteroaryl, heteroaryl (C₁₋₆) alkyl, heteroaryl (C₂₋₆) alkenyl and heteroaryl (C₂₋₆) alkynyl groups, wherein "heteroaryl" represents pyridyl, quinolyl, isoquinolyl, pyridazinyl, pyrimidinyl, pyrazinyl, pyranyl, furyl, benzofuryl, dibenzofuryl, thienyl, benzthienyl, indolyl, indazolyl, imidazolyl, benzimidazolyl, oxadiazolyl and thiadiazolyl.
 7. The method as claimed in claim 6 wherein the compound administered is selected from: 3-(1,2,3,4-tetrahydroisoquinolin-2-yl)methyl-1H-indole; or a pharmaceutically acceptable salt thereof. 